A SIMPLE METHOD FOR THE DETECTION OF THE TRANSPORT PATHWAYS OF MACROMOLECULES ACROSS ARTERIAL ENDOTHELIUM

血清大分子通过小窝和内皮间裂隙通过血管内皮层转运到血管内皮，但这些结构的渗透性的性质是未知的，并且小窝-囊泡转运的方式是有争议的。我们已经开发了一种优雅的方法，在固定和随机常规切片用于电子显微镜后使用原位示踪剂灌注来检测大分子通道。我们观察到的小窝和细胞间通道通过内皮层，只有少数人口的小泡游离在细胞质中，除了那些周围的高尔基区的动脉内皮。使用无偏形态测量，5%的腔外小窝和15%的细胞间裂隙形成跨内皮通道。在用N-乙基马来酰亚胺处理的大鼠腹主动脉中，细胞间通道以超过生理对照的6倍的频率从头形成;腔外小窝的密度降低至生理对照水平的80%，而较大的内陷数量增加。因此，我们建议，小窝通道，而不是转胞吞作用提供了一种机制的小窝囊泡运输在内皮细胞，因为转胞吞作用涉及许多自由囊泡，和一个灵活的通道系统功能广泛的大分子运输途径在动脉内皮细胞。

Serum macromolecules are transported through the vascular endothelial layer to the interstitium via the caveolae and interendothelial clefts, but nature of the permeability of these structures is unknown, and the manner of caveola-vesicle transport is controversial, We have developed an elegant method of detecting macromolecular channels using an in situ tracer perfusion after fixation and random conventional sectioning for electron microscopy. We observed the caveolar and intercellular channels through the endothelial layer, and only a few population of vesicles free in the cytoplasm except those around the Golgi area of the arterial endothelium. Using unbiased morphometry, 5% of the abluminal caveolae and 15% of the intercellular clefts formed transendothelial channels. In rat aortas treated with N-ethylmaleimide, intercellular channels formed de novo at a frequency more than six times that of the physiological controls ; the density of the abluminal caveolae was decreased to 80% of the physiological control level while the larger invaginations increased in the number. We therefore propose that caveolar channels rather than transcytosis provide a mechanism of caveola-vesicle transport in the endothelium, because transcytosis involves many free vesicles, and that a flexible channel system functions extensively as a macromolecular transport pathway in the arterial endothelium.